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Looking to buy, says lean needs tune

3K views 29 replies 7 participants last post by  Jesse Coles 
#1 ·
Im going to go look at a 2000 mustang 4.6L tomorrow and was told that the car starts no problem and drives as well as will pass a safety inspection but doesnt recommend driving it because of the mods making it run lean without a tune. This doesnt seem right to me that the mods he has would make the car run overly lean or outside of a factory tunes ability to compensate or just go into fuel rich limp mode so im looking for some opinions.



The mods he listed for the engine side are as follows:
engine :amsoil racing synthetic oil always and ford racing intake ,bbk78mm throttle intake , air aid cold air intake new spark plugs , new coils (originals included) will need a new tune as egr delete and h-vac delete where just installed , pace setter long tube headers and x pipe, under drive pullies ,and programmer .new alternator black one (original included) .......


Most of that is either irrelevant or wont cause this issue. The only things i can see being an issue is the EGR, Throttle Body, Cold Air (oil maybe getting on MAF) and/or Exhaust. Most i would think would either just put it in limp mode but maybe a cmbination of them is doing it? I am bringing a SCT Programmer with me but there is a chance (dont have it in my hands yet) that it is an updated firmware that removed the EGR delete option. I would have to drive it an hour home so curious if there is actually any reason to be afraid of engine damage from running lean.
 
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#2 ·
If the owner says don't drive it I wouldn't drive it in its current state. Trailer or tow dolly would be my recommendation to get it from point A to B. Running lean can raises combustion temps and you don't want to burn anything up.

The car is 20 years old and has some mods but if the price is right and you feel comfortable after looking at it, buy it.

I see this is your first post. Welcome to the forums.
 
#4 ·
I didnt think it would. I know the egr delete will immediately put the CEL on and if the exhaust he put on (long tubes and mid pipe) removed the second set of cats then again the CEL... but not lean. I'm thinking there is something else wrong with it. He wants 5000 CDN for it which would be steep but it comes with roll cage (not installed yet), new manual trans, new performance clutch, new fly wheel, new tires, full frame extensions, new rear control arms, 4.10 gears, new axles, lots of new suspension items, new short throw shifter, the throttle body, and a ton of other smaller mods that i am forgetting to list.


Thanks for the welcome! I used to have a pretty juiced up 86 mustang but never joined any forums.
 
#5 ·
the ford racing intake and the "cold air intake" probably require a tune to run right; that would explain the lean condition

I am more familiar with the S197 cars; but I assume the electronic fuel injection system in this car is similar: it depends on correct readings from the MAF (mass air flow) sensor to command the correct amount of fuel to give the correct A/F ratio for the air that is coming in. Many aftermarket intakes use a larger diameter air metering section (where the MAF sensor sits) and that larger diameter causes "incorrect" readings from the MAF sensor. There is more air actually coming in than the computer thinks is coming in (because the tube is bigger) ; and that's why it runs lean. The "tune" adjusts or "recallibrates" the MAF sensor readings so they tell the computer the correct amount of air that is coming in, and then the computer commands the correct amount of fuel to match, and it's no longer lean.

Headers also can require a tune because they move the O2 sensors further downstream, so again the signal that the computer is receiving is distorted and must be corrected with a "tune."

Generally in a computer controlled car, any time you make a change that affects the signals that are going to the computer, the computer program (aka "tune") needs to be corrected to match those changes.

I would be a bit concerned that the current owner has been driving it without correcting this situation; don't understand why they would do that.

EDIT: I am not sure if this car is "computer controlled" like the later ones, so I might be way off base!
 
#6 ·
I agree with JBert. "I would be a bit concerned that the current owner has been driving it without correcting this situation; don't understand why they would do that."
 
#7 ·
I'm about 95% positive that he hasnt because from the pictures of the documentation he sent, it hasnt been registered in 3 years. He says that is when he started all of these mods. Now like when i had to give up my last mustang, he is expecting a kid and is clearing out a ton of stuff.

I have a SCT X4 programmer that i got today (i work at a parts store so i can return it if i dont take the car) and am hoping that if i do take the car that the tune can be mostly corrected by that without having to do a dyno tune. Anyone have experience with these kinds of mods and those tuners? Every mustang i have ever built, which is a decent few, i have removed the FI and replaced it with a carb. My 86 was a carb converted roller that made an easy 423 rwhp but being a 2000, even though i can buy a carb conversion intake for the 4.6L, i think it would be best to leave it as FI.
 
#8 · (Edited)
What’s the “correction factor” or whatever it’s called for OBDII? Like how much fuel can the stock computer “tune” add or take away on its own? Surely more than OBDI, no? Why does an OBDI car not require a tune after an intake manifold swap?
A larger throttle body is not going to let more air in on a stock motor. Why? Because the air still gets “crammed back down” to the stock amount once it’s trying to go through the stock cylinder heads. Just like an hour glass. If you made the big parts of the glass bigger but not the skinny middle section the sand will still move empty out at the same rate. The skinny part of the hourglass is the cylinder heads. Cold air intakes, same thing as the TB. I guess if the MAF housing is larger then maybe the MAF “thinks” that there’s more air going into the cylinder heads than there really is? But even still it seems like the obdii ecu and all its glory would be able to compensate for the minuscule amount of extra that really is going in. Back in the early days of obdii, cold air intakes were all the rage (for all makes and models) but tuning wasn’t out there and “mainstream” like it is now. The “tune required” cold air intakes didn’t come around until handheld tuners were available for the masses. I don’t think the cai’s have changed, I think it’s a way to sell more crap. Some companies even sold “hot air intakes” that was pretty much just a conical filter sitting in the engine bay. Back then they were fine, but now they say that having an open filter in the bay can mess with the MAF readings so a tune is required. I went a butt-load of miles with a “hot air intake” and a gutted out cat in an OBDII car with no tune. I had a check engine light due to the cat, but it never ran bad. I’ve also heard people say that a tune is required with an X pipe because the o2’s have been moved. C’mon now, a tune with an X pipe!? Sorry to get on a rant on tuning, but sometimes it’s a little much. I’m not saying tuning doesn’t help, but I don’t think it’s required as often as the marketing team leads on. If a jinky OBDI ecu that can’t even “recognize” 93 and 87 octane and advance timing on its own can manage to not run lean with an intake manifold, surely the obdii ecu can add enough fuel to compensate for a cai. Think about it, an intake manifold can gain 15+ horsepower and a cai might can 6 on a good day. 15 hp worth of air is a lot more than 6.
How does the seller know it’s lean? Doesn’t he have a wideband O2 sensor? Or maybe data logging with a hand held scanner? Either way I’d take a pass. Sounds like buying a headache. His saying it’s lean sounds like he has a problem that he either doesn’t know how to fix or it’s n expensive fix. It’s not mega lean due to a plastic tube with a conical filter on the end, and I don’t think anyone has ever seen a 1/4 mile difference from a larger throttle body on a stockish motor. I can’t tell any difference with mine.
 
#9 ·
This is the list of mods that i might actually care about. It has a few that are going in the garbage if i buy it. Im thinking even if it has some engine troubles its still well worth the cash.

Engine:
- Ford Racing Intake
- BBK 78MM Throttle Body
- Cold Air Intake
- New Tune-up
- New Coils
- EGR Delete
- HVAC Delete
- Pace Setter Long Tubes
- Pace Setter X-Pipe
- Underdrive Pullies
- New Alternator
- New Radiator
- New Dual Electric Fans W/Controller

Transmission:
- Recently Rebuilt T45 5 Speed
- Manual Conversion
- Short Throw Shifter
- Ford Racing Flywheel
- Ford Racing Cobra Clutch
- Clutch Cable And Adjuster Upgrade
- Balanced Driveshaft w/New Yoke

Differential:
- New 4.10 Gears
- New Cobra Clutch Packs
- Axles Cleaned and Balanced

Suspension:
- 1.5" Lowering Springs
- Camber/Caster Plates
- Bump Steer Kit
- Alignment
- All New Shocks
- Aftermarket Rear Control Arms
- Full Length Frame Extensions
- Torque Box Reinforcements
- Upgraded Sway Bars And Bushings
- Welded In Rear Tower Brace
- Blot In Front Tower Brace

Other:
- Rebuilt Steering Rack
- Included But Not Installed Roll Cage
- 2004 Cobra Body Conversion
- ****** Aftermarket lights
- Cobra Center Console W/ DDIN
- Rear Battery Relocation
- Push Start Conversion
- Aftermarket Tail Lights
- After Market Headlights
- Cross Drilled Performance Brakes
- New E-Brake Cables
- Painted Black Stock Rims
- New Winter Tires
 
#10 · (Edited)
I could be mistaken but I think the ford racing manifold is just a stock replacement. When I google it all that comes up is the Ford brand P.I. mandiold which is what it came with from the factory. The ford performance manifold has a metal coolant crossover where the oem was plastic. So more than likely the oem one broke and leaked so he replaced it with the ford racing. If indeed that’s the manifold that it has, it’s not a performance upgrade exactly. It'll flow the same amount of air as stock. The throttle body is probably a little on the large side, maybe not, but there’s not going to be much if any extra horsepower with it. The long tube headers and X pipe might be good for some power, but it’s not going to be fast enough to where you’ll need the roll cage due to track rules. You know if you’re going X speed or X elapsed time you’re required to have a roll cage or they won’t let you race, well it won’t be anywhere near that fast. New clutch and rebuilt transmission- Sounds like he was beating the sht out of it and had to replace. He can’t exactly blame the clutch and trans going out due to too much power. He was probably power shifting, not letting off the gas between shifts. I bet the clutch went as well as the 1st-2nd synchros.
I had a Foxbody that was lowered about 1.5” with Eibach sportlines and it rode like a chuck wagon. Ask what brand the suspension stuff is: shocks/struts, springs, and rear control arms.
The push button start- I imagine you’ll still have to insert the key into the ignition and turn it forward and then press the button. So there’s actually more steps involved to start it vs just turning the key.
None of those mods would make it lean enough to be worth mentioning. Think back to your carb cars. Would you have to change carb jets after the addition of a gauze (k&n type) filter vs a paper one? That’s pretty much what’s going on here. It won’t be anything like your 420 horse fox. If you want to go faster with these your options are cam upgrades that are good for a little, or forced induction that’s good for a lot but kind of pricey. There’s no aftermarket heads really and bolt-ons yield similar performance as they would on your fox.
I’d run for the hills. He probably beat on it pretty hard, he says it’s lean, and it’s not going to be that fast. I think you’re buying someone’s headache along with led lights and a body kit.
https://m.youtube.com/watch?v=MRvPHxHC8qQ
*Edit*
It hasn’t been registered in three years!? I just saw that. Man, you don’t want that thing. Pacesetter is at the lower end of the “quality scale” so chances are it might have no name (SVE, SR Performance, etc) control arms. Maybe even the springs too. Ask for brands.
 
#13 ·
Thanks for all the info guys, i went and looked at it and found out the guy was a complete idiot. For whatever reason he decided to "delete" the Evap system... When he did it he left a very obvious vaccum line hanging out sucking air. We had a snap-on scanner and read it while running and both O2 sensors were toast and he didnt have a proper hose setup for the intake so the mass air wasnt reading correctly. The "lean condition" of the car was so lean it burned your eyes with the raw fuel it was dumping out of the exhaust lol. So got it home put a temp intake hose on it (getting silicone replacements tomorrow), ordered 2 O2 sensors and plugged the vacuum leak. Motor still rich because of the O2 sensors but it is running semi normal now. I think he just deleted the evap and said he installed used O2 sensors and when the car wouldnt idle anymore, event hough all you can smell is fuel, thought it was running lean and decided to sell it when he couldnt figure it out.

His battery relocate was done good with the wires but he just took a trailer box and tossed a battery in it, didnt even secure it into the trunk lol. So i ordered a proper taylor box for tomorrow. The headlights were trash, he cut out a projector from a BMW and installed something he called a Demon Eye Bluetooth kit in them so i sold them back to him because i was going to throw them in the trash. So i had to buy 2 head lights, a bumper (he sold it and didnt mention that in the ad and pics showed the bumper but meh) and i think im going to be off to the races


And i know these things arent like the 5.0s of old or even new for that matter. Not looking for 420 horse anymore. Something quick and decent looking and reliable. I think i can get this thing to 300 or 320 rwhp with cams and some other bits and be happy and done.
 
#16 ·
It's even worse. I was in the trade for 7 years and my friend was in for 25 years and owned his own shop and this guy argued with us and played the "I know what im talking about, im a 4th year automotive apprentice" lol! In Canada we have an apprenticeship program where you have to go through 4 years, have a certain amount of hours and do 4 years of school, 2 months a piece before you get certified. Scary that we have a program like this in place to weed out chaff and this one slipped through. I think he screwed himself out of something good and a lot more money had he knew what he was doing and sold it running.
 
#19 ·
A lot of guys never realize that bolting on a "good part" won't make your car faster necessarily. "Hey, I have a 400MM throttle body on my 2V!" - well, great. Now your engine has enough air. But even if you calibrate it to the Nth degree, and get the mix right, you still have restrictive heads, cams, exhaust, intake, etc!



Making your car fast requires an understanding of how all the parts work together, and producing power in the RPM range you're actually going to use. Even a person that is mostly 'smart' can get caught up in the "Well, I might as well get the bigger one, since they're the same price..." game though. I know I have. Not that I'm too smart apparently. *laughing
 
#26 ·
A lot of guys never realize that bolting on a "good part" won't make your car faster necessarily. "Hey, I have a 400MM throttle body on my 2V!" - well, great. Now your engine has enough air. But even if you calibrate it to the Nth degree, and get the mix right, you still have restrictive heads, cams, exhaust, intake, etc!

Making your car fast requires an understanding of how all the parts work together, and producing power in the RPM range you're actually going to use. Even a person that is mostly 'smart' can get caught up in the "Well, I might as well get the bigger one, since they're the same price..." game though. I know I have. Not that I'm too smart apparently. *laughing
...oh how I remember in HS...everyone thought that sticking an 800 cfm carb is going to make your car run soooo fassssst! except my dad taught me so much about cars long befor I got my license...I never got sucked into that stuff of idiots!
 
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#21 ·
Here's how I understand it:
> EFI works by measuring how much air is coming in, and commanding the right amount of fuel to go with it
> The MAF (Mass Air Flow) Sensor measures the velocity of the air, where the sensor sits; and then the computer uses math to convert the velocity to mass flow rate
> to do that math, the computer needs the diameter of the tube where the MAF is reading the velocity . . . simplified math is velocity times area = volume flow rate (volume per unit time) ; volume flow rate times density = mass flow rate (the air/fuel mix math is actually done on mass)
> the "mass air metering section" is the tube where the MAF sensor sits -- it is the diameter of this section that is important for the math
> when they increase the diameter of the tube, from say 70 mm to 100 mm; this usually includes the entire tube, including the mass air metering section
> there are some intakes that use an insert in the MAF metering section, to neck it down to the original diameter, to avoid the need for a tune; then you can remove the insert, which removes that restriction, then you need a tune
> if the computer is doing the math based on 70 mm diameter (3848 mm^2 area) but the tube is actually 90 mm diameter (6361 mm^2 area) the volume and math calculation is going to be off by a factor of about 1.7 (6361/3848), which is way more than it can adjust for by using the O2 sensor readings
 
#22 ·
What if the intake opening is smaller than the MAF metering section, does that throw the math off? If the MAF is 100mm and the intake opening is only 70mm and the MAF “thinks” that there’s “100mm worth of air” going in but there’s really only 70mm would that not cause a rich condition? Maybe the “canned tunes” sort it out to where it’s only adding enough fuel for the actual“70mm worth” of air going in? Is that the “required tune” part, so it doesn’t add more fuel than it really needs? I get it that a larger tube will have less velocity than a smaller one so a tune is required to correct that. But the cold air intake mfgs and vendors say that it will run lean without a tune don’t they since “more air is going in” so they need to add more fuel? If the intake opening hasn’t changed sizes and the air isn’t being forced in, how is more air really getting in?
 
#25 ·
I am way out of my depth on the specifics of intake manifold design so I won't attempt to get into the details . . .

but the basics still hold: the system needs a correct measurement of how much air is coming in. All of the restrictions in the entire system, including any neck-down point anywhere in the flow, will determine how much air comes in. For the purpose of the air/fuel mixture, it does not matter what is the restriction that is limiting the air flow; it only matters that the computer has a correct reading of how much is coming in.

The whole point is to deliver the correct air/fuel ratio. The new system with a modified intake might flow more or less air; if it flows more air it will need more fuel, if it flows less air it will need less fuel; whatever it is, the computer needs the correct readings to command the correct amount of fuel for the correct air/fuel ratio. The tune is simply to give the computer the correct information; not to push more fuel if the system doesn't actually need it.

I was not talking about whether the modified intake will flow more air or not, that is a much different conversation. I was only talking about why most aftermarket intakes need a tune.

But, regarding how an improved intake can flow more air through the system, even if the downstream restrictions are not changed: the basic principle is, all fluid flow is driven by pressure differentials. The air is actually pushed into the cylinders by atmospheric pressure, less the pressure drop through the intake system. A "cold air intake" with less restriction will have less pressure drop, so more pressure will reach the throttle body. So even though there could be restrictions at the throttle body and downstream, there can be more air flowing through the whole system because the pressure drop through the "cold air intake" is reduced.

A modified hourglass analogy would be if your were blowing air through the restriction. If you blow harder, more air goes through. An improved "cold air intake" is basically blowing harder on the throttle body.
 
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#27 ·
90LXwhite, your hourglass explanation is dead on. But what we *don't* know for sure is where the original 'smallest point' was. If in fact, the MAF was the original restriction, then increasing the size of the MAF would definitely allow more air to flow. Even so, the new MAF should account for that. My bet? The new MAF isn't as accurate as the old one, so it's not detecting all the incoming air as well, especially at low RPMs. Since it doesn't notice some of the air sneaking by, it's not adding more fuel, causing a lean condition.


Equally likely: The O2 sensors need to be replaced, and they're giving false readings about lean/rich condition.
 
#28 ·
Big oooof... everything on the car seems good and worth the money i paid i think. Putting on actual intake hose instead of whatever he was using, plugging a vacuum leak, replaced the O2 sensors (both had heater circuit fault) and fired it up. Took about 2 minutes of holding the gas a bit then it idled perfectly on its own. After 10 mins of idling it started reving to 2000 and then almost stalling so on goes the scanner and i get both O2 sensors heater circuit failure still. Watched the data from the o2s and ive never seen such a thing in my life, One sensor is dead flat at 0v which isnt all that crazy, could just be a broken wire connection somewhere. The wierd part was the other sensor. It was cycling irregularly and with large pauses and at an extremely low voltage, 0v-0.1v.



Started following wires and found some creative non-factory wires here and there.There was one wire that seemed really out f place so we clipped it thinking it was his dumb attempt at putting in an AF meter and still had circuit fault but the one sensor that was cycling stopped cycling and started this really odd stairway pattern. We watched it for about 3 minutes and shut the car off. It would step up the tiniest bit hold, then step up again from 0v-0.6v. We reset the ect tune to stock in case he messed with any settings and there was no change.



Judging from the creative wiring we've seen now that we have it up on a hoist tells me we are in for a fun ride undoing whatever this professional 4th year apprentice has done, lol. Wish me luck, looking at it again tonight and im hoping i have some bad fuses and not that he crossed something and fried something in the ecm.
 
#30 ·
Going decent so far. Only get an hour or so a night to work on it. I got the tune fixed, vacuum leaks fixed, undid whatever it was he was trying to do with the power steering so now i have steering and brakes. Its purring like a kitten. Just have to figure out this damn O2 issue. Its actually cycling 0c-0.03v not 0.3v and now when i rev it up it goes open loop and sits at 0.9v full rich even though you dont smell any extra gas on the exhaust anymore at all. he also cut the cat back into 3 pieces for each side and then left out a piece so i have to buy a new cat back basically. The joys of modified mustang ownership, if you dont buy it with problems, you'll likely make problems at the track anyway :)
 
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